Unhairing bath and process of treating hides



Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE.

NORMAN D. HARVEY, JR., PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO CARBIDE & CARBON CHEMICALS CORPORATION, A CORPORATION OF NEW YORK UNHAIRING BATH AND PROCESS OF TREATING HIDES No Drawing.

The invention relates to baths for unhair-- ing hides. Such baths are useful in recovering wool or other hair for textile purposes, but their principal application is in the preparation of hides for tanning.

Hides are normally delivered at the tanner v after curing by salting or sun-drying. At the tannery the hides are soaked to cleanse and rehydrate them. They are then unlo haired, phunped, and finally tanned.

The unhairing and plumping operations, as a rule. are carried out together, as by treating the hides for two or three days in a bath prepared by suspending lime in water, and

13 then adding sodium sulphide. Such a bath decomposes the epidermis, or outer layer of the hide; and since the epidermis lines the hair follicles and grips the hairs the latter are loosened so that they can be removed me- So chanically. At the same time the corium (which lies under the epidermis and forms the substance of the finished leather) swells, takes on a tirmer texture, and is otherwise so modified that it becomes amenable to tan- :3 nine. This effect is called plumping. An alkalinity represented by pH at least is required tor unhairingr, but a higher alkalinity promotes the process. Plumping requires pl-l at least about 12, while 12.5 gives better :to results. If plumpiu; proceeds too rapidly, so that it outstrips the disintegration of the epidermis, the coriun'rcloses on the roots of the hairs and prevents proper loosening of the latter. it; In accordance with the invention, monoethanol amine is used as an unhairing agent. For example. the. hid-es may be covered with an aqiteous solution of monoethanol amine of such concentration that about one 40 pound of amine is present for each 100 pounds of hides: but the proportion of amine to hides d5 Monoethanol amine has only a .feeble ciency during use.

Application filed March 21, 1930. Serial No. 437,942.

plumping action; and it may advantageously be used in conjunction with more strongly alkaline agents having pronounced Plumping properties, such as the hydroxides or sulphides of the alkali and alkaline earth metals. Certain other amines, such as methyl amine and ethylene diamine have both plum ping and unhairing properties and may be admixed with monoethanol amine. A bath containing the proportion of monoethanol 5 amine mentioned above (one pound per hundred pounds of hides) with about 10 pounds of lime per hundred pounds of hides has very good unhairing and plumping properties.

Like known unhairing baths, those containing monoethanol amine increase in efli- This appears to be due to the in orporation of substances extracted from the hides. Among the substances which give rise to the increased efficiency, monoet-hanol amine sulphide formed by the interaction of the bath with hide proteins seems to be one of the most important.

\Vhen used in conjunction with lime, monoethanol amine promotes absorption of the 7 lime by the hides. Hides treated with such a mixture are lighter in color, and have a finer and thicker grain than hides treated with the usual lime-sulphide compositions.

\Vhen wool is to be removed from sheepskins, a less alkaline bath, such as one containing monoethanol amine alone, may be used. Whereas the usual agents for this purpose dissolve the roots of the hairs, it is possible with monoethanol amine baths to so loosen the hairs without destroying the root, or portion embedded in hide. The fibre length and poundage of the WOOl recovered are thus increased.

I claim:-

1. An unhairing bath containing monoethanol amine and a plumping agent.

2. An unhairing bath containing monoethanol amine, and an inorganic compound of alkaline reaction.

tso

3. An unhairing bath containing monoethanol amine and lime.

4. An unhairing bath containing monoethanol amine and lime in the proportions of approximately one pound to ten.

5. The process of treating hides to remove hair therefrom which consists in soaking the hides in a bath containing monoethanolamine until the hairs are loosened.

6. The process of treating hides to remove hair therefrom which consists insoaking the hides in a bath containing monoethanolamine and lime until the hairs are loosened.

In testimony whereof, I afiix my signature.

NORMAN D. HARVEY, JR. 

